Network and topology for identifying, locating and quantifying physical phenomena, systems and methods for employing same

ABSTRACT

A method and system for detecting, locating and quantifying a physical phenomena such as strain or a deformation in a structure. A plurality of laterally adjacent conductors may each include a plurality of segments. Each segment is constructed to exhibit a unit value representative of a defined energy transmission characteristic. A plurality of identity groups are defined with each identity group comprising a plurality of segments including at least one segment from each of the plurality of conductors. The segments contained within an identity group are configured and arranged such that each of their associated unit values may be represented by a concatenated digit string which is a unique number relative to the other identity groups. Additionally, the unit values of the segments within an identity group maintain unique ratios with respect to the other unit values in the identity group.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.10/074,355 entitled SYSTEMS AND METHODS FOR COATING CONDUIT INTERIORSURFACES UTILIZING A THERMAL SPRAY GUN WITH EXTENSION ARM, filed on evendate herewith.

GOVERNMENT RIGHTS

The United States Government has rights in the following inventionpursuant to Contract No. DE-AC07-99ID13727 between the U.S. Departmentof Energy and Bechtel BWXT Idaho, LLC.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a network and topology fordetecting physical phenomena and for locating and quantifying the same.More particularly, the present invention relates to the use of a codednetwork implemented within a structure for detecting physical changeswithin the structure.

2. State of the Art

It is often desirable to detect and monitor physical changes within astructure. For example, it may be desirable to monitor pipes or otherconduits for leaks or indications thereof so as to prevent collateraldamage from such leaks. Similarly, it may be desirable to monitor thedeformation of other structures, such as, for example, a bridge, abuilding, or even individual structural components of such facilities inorder to determine actual or potential failures therein.

Various systems have been used to detect such physical changes. Forexample, one system used for detecting leaks in a pipe or other conduitis disclosed in U.S. Pat. No. 5,279,148 issued to Brandes on Jan. 18,1994. The Brandes patent teaches a system which includes a first pipefor carrying a liquid medium and a second pipe which is coaxiallylocated relative to the first pipe such that it encompasses the firstpipe. A filler material is disposed in the annulus formed between thefirst and second pipes. Probes are inserted into the filler material ateach end of the set of pipes to measure resistance of the fillermaterial at each end of the pipe system relative to ground as well asbetween the two ends of the pipe system. Initial resistance measurementsare used as a baseline value for future monitoring. Detection ofsignificant deviation in the resistance measurements indicates a leakfrom the first pipe (i.e., the liquid medium has infiltrated the fillermaterial thereby changing the resistivity/conductivity thereof). Thechange in resistance between the ends of the coaxial pipes as well asthe change in resistance at each end of the coaxial pipes relative toground may then be utilized to determine the location of the leak bycomparing the ratio of the respective changes in resistance.

While such a system may be effective in detecting a leak within a pipe,it may also be cumbersome and expensive to implement, particularly sincea second outer pipe is required to encapsulate the filler material aboutthe liquid carrying pipe. Such a system would likely be difficult andcost prohibitive in retrofitting an existing layout of pipes or otherconduits for leak detection. Also, the Brandes patent fails to disclosewhether such a system would be effective for structures extendingsignificant distances (i.e., several miles or longer) and with whatresolution one may determine the location of a detected leak.

Further, such a system is only practical with respect to detecting afailure in a liquid carrying structure. If a transported liquid is notavailable to infiltrate the surrounding filler material andsignificantly change the electrical properties thereof, no detectionwill be made. Thus, such a system would not be applicable to detectingfailure in various members of bridges, buildings or other suchstructures.

Another method of detecting fluid leaks includes the use of time domainreflectometry (TDR) such as is disclosed in U.S. Pat. No. 5,410,255issued to Bailey on Apr. 25, 1995. TDR methods include sending a pulsedown a transmission line and monitoring the reflection of such pulses. Achange in the time of arrival or the shape of a reflected pulseindicates a leak based on, for example, a change in the structure of thetransmission line and/or its interaction with the leaking medium.However, to implement a TDR system with, for example, a pipeline whichextends for significant distances, special processing algorithms mayhave to be developed to enable rejection of spurious data for pipejoints or other discontinuities. Also, the types of transmission lineswhich may be used in such a TDR system may be restricted based on theirelectrical characteristics including the dielectric and resistivitycharacteristics of any insulation associated with such transmissionlines.

Yet another approach detecting fluid leaks is disclosed in U.S. Pat. No.4,926,165 to Lahlouh et al. on May 15, 1990. The Lahlouh patent teachesthe use of two spaced apart conductors separated by a swellable membersuch that no electrical path exists between the two conductors in normaloperating conditions. Upon occurrence of a leak, the swellable memberswells to conductively contact the two conductors, creating anelectrical short therebetween as an indication of a leak. However, sucha device requires relatively complex construction including properconfiguration of the conductors and swellable members. Additionally, theintrusion of a liquid other than that which may potentially leak from apipe or conduit could trigger false indications of such leaks.

Additionally, as with the aforementioned Brandes patent, the method anddevice of the Lahlouh patent may only be used for detecting leaks in aliquid carrying structure and is not capable of detecting failures inother structures.

In view of the shortcomings in the art, it would be advantageous toprovide a method and system for detecting, locating and quantifyingphysical phenomena such as leaks, strain and other physical changeswithin a structure. Further, it would be advantageous to providemonitoring of such physical phenomena to track potential failures of astructure for purposes of preventative maintenance.

It would further be advantageous to provide a method and system fordetecting physical phenomena which is inexpensive, robust, and which maybe implemented in numerous applications and with varying structures.

BRIEF SUMMARY OF THE INVENTION

In accordance with one aspect of the invention a method of monitoring astructure is provided. The method includes attaching a plurality oflaterally adjacent conductors to the structure and defining eachconductor of the plurality to include a plurality of segments coupled inseries. Each of the segments are defined to have an associated unitvalue which is representative of a defined energy transmissioncharacteristic. A plurality of identity groups is defined wherein eachidentity group includes a plurality of laterally adjacent segments andwherein each identity group includes at least one segment from each ofthe plurality of conductors. Energy is transmitted through the pluralityof conductors and the plurality of conductors is monitored for a changein the defined energy transmission characteristic. A change in thedefined energy transmission characteristic of one conductor may then becompared to the change in the defined energy transmission characteristicto at least one other conductor

The method may further include determining from which identity group thechange in the defined energy transmission characteristic originated. Thedetermination of the originating identity group may include determiningratios of the change in the defined energy transmission characteristicfrom one conductor to another and comparing the ratios with a set ofpredetermined ratios which correspond to the ratios of unit valuescontained in individual identity groups.

In accordance with another aspect of the invention, a method is providedfor detecting and monitoring a physical phenomena, such as, for example,strain induced within a structure. The method includes attaching aplurality of laterally adjacent conductors to the structure such that aphysical phenomena exhibited by the structure in response to an appliedphysical condition will be substantially detected by the plurality ofconductors. Each of the plurality of conductors is configured to exhibita change resistance upon experiencing the physical phenomena. Eachconductor is also defined to include a plurality of segments with eachsegment exhibiting an associated resistance value of the defined energytransmission characteristic. A plurality of identity groups is definedsuch that each identity group includes a plurality of laterally adjacentresistance segments and such that each identity group includes at leastone resistance segment from each conductor. Energy is transmittedthrough each of the plurality of conductors and each of the conductorsis monitored for a change in resistance. A detected change in resistanceof a first conductor is then compared to a change in resistance of atleast one other conductor.

In accordance with another aspect of the present invention, a system fordetecting physical phenomena in a structure is provided. The systemincludes a plurality of laterally adjacent conductors with eachconductor including a plurality of segments and wherein each segment isdefined to have an associated unit value representative of a definedenergy transmission characteristic. A plurality of identity groups isdefined such that each identity group includes a plurality of laterallyadjacent segments including at least one segment from each conductor.Each segment within an identity group is defined to exhibit anassociated unit value such that the unit values in each identity groupmay be represented by a concatenated digit string of the unit values.Each identity group is defined so as to exhibit a unique concatenateddigit string relative to the other identity groups.

In accordance with another aspect of the present invention, a structureis provided. The structure includes at least one structural memberhaving a plurality of conductors attached thereto. Each conductor of theplurality includes a plurality of segments. A plurality of identitygroups is defined such that each identity group includes a plurality ofsegments including at least one segment from each conductor. Eachsegment within an identity group is defined to exhibit an associatedunit value representative of an energy transmission characteristic suchthat the unit values of each identity group may be represented by aconcatenated digit string of the unit values contained therein. The unitvalues are further defined such that each concatenated digit string isunique.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings in which:

FIG. 1 is a schematic of a network and topology used in detecting aphysical phenomena according to one embodiment of the present invention;

FIG. 2 is a schematic view of a portion of the network shown in FIG. 1;

FIG. 3 is a partial cross-sectional view of a structure incorporating anetwork according to an embodiment of the present invention;

FIGS. 4A and 4B are partial sectional views taken along the linesindicated in FIG. 3; and

FIG. 5 is a partial cross-sectional view of a structure and anassociated network for detecting physical phenomena according to anaspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a network 100 is shown for detecting a physicalphenomena according to an exemplary embodiment of the present invention.The network 100 includes a transmitter 102 operatively coupled with afirst conductor 104 and a second conductor 106 at first adjacent endsthereof. The two conductors 104 and 106 are each coupled at an opposingend to a receiver 108. The conductors 104 and 106 may be any of a numberof different energy transmitting mediums, including, for example,conductive traces, semiconductive traces or optical fibers and, thus,the term “conductors” is used herein to encompass any such energytransmitting medium. Similarly, while the terms “transmitter” and“receiver” are used herein, such are used in the generic sense of beingable to transmit energy (including, for example, electrical energy orlight energy) and receiving and detecting the transmitted energy.

The first and second conductors 104 and 106 are positioned laterallyadjacent one another and are defined to include a plurality of segments110A-110D and 112A-112D respectively which, for sake of convenience,shall be referred to herein with respect to the exemplary embodiments asresistance segments. As with the various terms discussed above, the term“resistance segment” is used generically to indicate a defined level ofresistance to the energy flow which is being transmitted through theconductors 104 and 106.

Furthermore, while the exemplary embodiments discuss the use of“resistance segments,” the present invention may be practiced with aplurality of segments wherein each segment is defined to exhibit a unitvalue which is representative of a specified energy transmissioncharacteristic other than resistance to energy flow. Additionally,discussion below with regard to the exemplary embodiments of detectingor measuring “changes in resistance” is equally applicable to detectingand measuring a change in the specified energy transmissioncharacteristic.

Referring still to FIG. 1, the resistance segments 110A-110D of thefirst conductor 104 are operatively connected in series with oneanother. Likewise, the resistance segments of the second conductor 106are operatively connected in series with one another. It is noted that,while the exemplary embodiment of the network 100 is shown using twoconductors 104 and 106 with each having four resistance segments110A-110D and 112A and 112D respectively, the invention may be practicedwith other combinations of conductors and resistance segments as shallbe discussed in greater detail below.

A plurality of identity groups 114A-114D are formed of laterallyadjacent resistance segments 110A-110D and 112A-112D respectively. Thus,identity group 114A comprises resistance segments 110A and 112A,identity group 114B comprises resistance segments 110B and 112B and soon.

Referring to FIG. 2, and using an example of conductors 104 and 106comprising conductive traces or other electrically conductive members,the resistance segments 110A-110D and 112A-112D are assigned exemplaryunit resistance values, in this case expressed in the unit ohms forelectrical resistance. The assigned, or defined unit resistance valuesare as shown in FIG. 2 with resistance segment 110A having a unitresistance value of 1 ohm, resistance segment 112A has a unit resistancesegment of 4 ohms, and so on. Further, each identity group may beidentified by a concatenated digit string which is representative of theactual or normalized unit resistance values contained therein. Thus,identity group 114A may be represented by the digit string “14” based onthe unit resistance values for resistance segments 110A and 112A.Similarly, identity group 114B may be represented by the digit string“23”, identity group 114C by the digit string “32” and identity group114D by the digit string “41.”

It is noted that the concatenated digit string for each identity group114A-114D is a unique number in comparison with the concatenated digitstrings for every other identity group within the network 100. Further,it is noted that the ratios of the unit resistance values within a groupidentity are likewise unique. For example, the ratio of unit resistancevalues in identity group 114A is 1:4 or 0.25. In comparison, the ratiofor identity group 114B is 2:3 or 0.667, for identity group 114C is 3:2or 1.5 and for identity group 114D is 4:1 or simply 4. The identity ofsuch ratios, as well as the uniqueness each of the various ratios,assist in detecting, locating and quantifying a physical phenomena asshall become more apparent below.

Referring to FIG. 3, a network such as described above is incorporatedinto a structure 120 which, in the exemplary embodiment, is shown as aconduit 122 such as, for example, a part of a pipeline for carrying afluid medium. The network 100 is formed on the interior surface 124 ofthe conduit 122, although other locations, including the exterior of thepipeline, are also suitable. Generally, the network 100 may be formed onthe surface of, or embedded within, any of a number of differentstructures, which may be referred to more generically as a substrate.

In the case of a pipeline or conduit 122, it may be desirable to detectstrain or deformation within the structure 120 so as to determinepotential failures which, in this case, may result in leakage of fluidfrom the conduit. Thus, for example, if the conduit 122 exhibitsdeformation or strain in an area associated with identity group 114B,resistance segments 110B and 112B, which are coupled with the surface124 of the conduit 122, will likewise exhibit the strain or deformation.If the conductors 104 and 106 are electrical type-conductors, theresistance segments 110B and 112B will exhibit a change in resistivityupon experiencing an induced strain. Thus, a change in resistancemeasured across the conductors 104 and 106 indicates a deformation inthe structure. It is noted that if the conductors are positioned closelyenough, a substantial deformation in the structure 120 to which they areattached should induce strain in both conductors 104 and 106. Thus,certain anomalies wherein a resistance change in one conductor 104 butnot another 106 may be substantially accounted for.

It is also noted that if the conductors 104 and 106 are of a differenttype of energy transmitting medium, such as, for example, opticalfibers, some other property will exhibit a change, such as a phasechange of the light signal traveling through optic fibers, uponexperiencing a strain therein.

Furthermore, while the exemplary embodiments set forth herein aredescribed in terms of detecting strain or transformation, other physicalphenomena may be detected, located and quantified. For example, thephysical phenomena may include changes due to temperature, corrosion,wear due to abrasion, chemical reactions or radiation damage asexperienced by the conductors.

Still using electrical conductors 104 and 106 as an example, the changein resistivity in each resistance segment 110B and 112B will be afunction of the unit resistance values respectively associatedtherewith. By determining the ratio of the change in resistance measuredby a receiver 108 through each of the conductors 104 and 106, thelocation of the strain may be determined.

For example, referring back to FIG. 2, a strain induced in theresistance segments 110B and 112B of identity group 114B will result ina change of resistivity in each conductor 104 and 106. It is noted thatupon initial implementation of the network 100 the overall resistance ofa conductor 104 and 106 may be measured and utilized as a baselinevalue. Any subsequent measurements of resistance may then be compared tothe baseline value to detect whether a change in resistance has occurredor not. The conductors 104 and 106 may be checked for resistance changesat a predetermined sample rate, such as, for example, once per second.Of course other sample rates may be utilized according to specificapplications and monitoring requirements.

It may be the case that once a change in resistance has been detectedthat the measured value of resistance may not return to its originalbaseline value. For example, a change in resistance may be due to apermanent deformation in an associated structure. Thus, it may berequired to set a new baseline value (or re-zero the values) of theoverall measured resistance in the conductors 104 and 106 after thedetection of a change in resistance.

The measured change in resistance detected in the conductors 104 and 106is a function of the unit resistance values of the individual resistancesegments 110B and 112B (e.g., it is a function of, in this exampleproportional to, the values of 2 ohms and 3 ohms respectively). Thus, bytaking the ratio of the change in resistance measured by the receiver(i.e., ΔR₁₀₄/ΔR₁₀₆, where ΔR is the change in resistance for thespecified conductor), the ratio may be compared to the ratios of theunit resistance values of each identity group 114A-114D to determine thelocation of the strain. In this case, strain exhibited in the regionencompassed by identity group 114B will exhibit itself as a change inresistance in both conductors 104 and 106, the ratio of which changewill be a function of the ratio 2:3 or 0.667 which is equal to the ratioof the unit resistance values thereof. The detection of strain ordeformation within identity groups 114A, 114C or 114D would likewiseyield, with regard to the change in resistance in the conductors 104 and106, functions of the ratios 0.25, 1.5 and 4 respectively.

Having located the area of deformation (e.g., within identity group114B) the magnitude of the strain may then be calculated. As will beappreciated by one of ordinary skill in the art, the change inresistance measured by the receiver 108 for a particular conductor 104or 106 is a function of the unit value resistance associated with theresistance segment (e.g. 110B or 112B) in which the strain was detected.Thus, by knowing the unit value of resistance for a particularresistance segment in which strain has been detected, the amount ofchange in resistance exhibited by a conductor and the relationshipbetween strain and resistance for a conductor of a given configurationand material composition, one can calculate the amount of strainexhibited by the conductors 104 and 106 and thus the amount of straininduced in any associated structure 120 to which they are attached.

For example, having located a strain in identity group 114B, andassuming the use of electrical traces for conductors 104 and 106 andassuming linear proportionality between change in resistance and unitresistance, one could determine the magnitude of the strain using thefollowing equations:${{DEFORMATION} = {\frac{\delta\quad{ɛ(R)}}{\delta(R)}\frac{\Delta\quad R_{104}}{2}\quad{for}\quad{the}\quad{strain}\quad{exhibited}\quad{in}\quad{conductor}\quad 104}},{{and};}$${DEFORMATION} = {\frac{\delta\quad{ɛ(R)}}{\delta(R)}\frac{\Delta\quad R_{106}}{3}\quad{for}\quad{the}\quad{strain}\quad{exhibited}\quad{in}\quad{conductor}\quad 106\quad{where}}$ε(R) is represents the relationship between resistance and strain for agiven resistance segment, ΔR represents magnitude of the change ofresistance measured in a given conductor and wherein the numeraldenominator represents the unit resistance value for the particularresistance segment in which strain was detected (i.e., the “2” in thefirst equation is for resistance segment 110B, and the “3” in the secondequation is for resistance segment 112B).

As has been noted above, one embodiment may include the use ofconductive traces for conductors 104 and 106. Referring to FIGS. 4A and4B, a partial cross-sectional view is shown of conductors 104 and 106utilizing conductive traces according to one embodiment. As is indicatedin FIG. 3, FIG. 4A is a view depicting the resistance segments inidentity group 114C while FIG. 4B is a view depicting the resistancesegments in identity group 114D.

The conductors 104 and 106, shown as conductive traces, may be attachedto a structure 102, such as the conduit 122, by a thermal spray process.In order to apply the conductive traces to a structure 120, includingone in which the surface may be degraded and/or conductive, it may bedesirable to provide an insulative layer 132 directly on the surface 124of the structure (e.g., the conduit 122). The insulative layer 132 keepsthe conductors 104 and 106 from forming an electrical connection withthe structure 120, and also provides a uniform surface on which to formthe conductors 104 and 106. One insulative layer 130 may be formed andsized such that all of the conductors 104 and 106 may be formed thereonor, alternatively, an individual layer 130 may be formed for eachindividual conductor 104 and 106 as may be desired. A second insulativelayer 132 may be formed to encompass or encapsulate the conductors 104and 106 from each other and from the surrounding environment. It isnoted, however, that if physical phenomena such as corrosion or abrasionis being detected, located and/or quantified, that the second insulativelayer 132 would not be needed.

Such an embodiment as shown in FIGS. 4A and 4B may include, for example,an insulative layer 130 formed of alumina, conductive traces ofnickel-aluminum, and a second insulative layer 132 of alumina. Othermaterials may also be suitable such as, for example, copper or otherconductive materials for the conductors 104 and 106. Likewise othermaterials may be utilized in forming the insulative layers 130 and 132.

An embodiment such as that shown in FIGS. 4A and 4B may be formed bythermal spraying of the insulative layers 130 and 132 and/or theconductive traces (which form the conductors 104 and 106). In oneexemplary embodiment, a thermally sprayed insulative layer 130 may beapproximately 0.5 inches wide and 0.12 to 0.15 inches thick. Aconductive trace acting as a conductor 104 or 106 may be formed with awidth of approximately 0.3 inches and a thickness of approximately 0.007inches. One such exemplary conductive trace was formed on the interiorof an eight inch long piece of square tubing and exhibited an electricalresistance of 4.1 ohms under no-load conditions. The same conductivetrace exhibited a change in resistance to approximately 38 ohms when thetubing was subjected to three-point bending with a loading ofapproximately 40,000 pounds. The conductive trace returned to 4.1 ohmsupon removal of the three-point bending load.

An exemplary thermal spraying device which may be used in conjunctionwith the application such insulative layers 130 and 132 and/orconductors 104 and 106 is disclosed in pending U.S. patent applicationSer. No. 10/074,355 entitled SYSTEMS AND METHODS FOR COATING CONDUITINTERIOR SURFACES UTILIZING A THERMAL SPRAY GUN WITH EXTENSION ARM,filed on even date herewith and which is assigned to the assignee of thepresent invention, the entirety of which is incorporated by referenceherein.

Referring briefly to FIG. 5, the conductors 104 and 106, when in theform of electrical conductive traces, may be formed by building upindividual layers 140A-140G until a desired thickness or height of theconductors 104 and 106 is obtained. Likewise, if so desired or needed,the insulative layers 130 and 132 may be layered to obtain a desiredthickness or height. Further, if so needed, a bonding agent or bondinglayer 134 may be used between the insulative layer and a surface 136 ofthe structure 120 if the surface exhibits a degree of degradation.

As can be seen by comparing the conductors 104 and 106 from FIG. 4A toFIG. 4B the conductors 104 and 106 may vary in cross sectional area fromone resistance segment to another (i.e., from 110C to 110D and from 112Cto 112D). The change in cross-sectional area of the conductors 104 and106 may be effected by varying their width (such as shown), their heightor some combination thereof. Of course other cross-sectional areas arecontemplated and the variance thereof may depend on other variables,such as for example, a diameter of the cross-sectional area.

Changing the cross-sectional area of the conductors 104 and 106 is oneway of defining unit resistance values for the plurality of resistancesegments 110A-110D and 112A-112D. Alternatively, the unit resistancevalues may be defined by utilizing different materials or varying thematerial compositions for the individual resistance segments 110A-110Dand 112A-112D. For example, a first resistance segment 110A may beformed of a first material exhibiting a first resistivity while the nextadjacent resistance segment 110B may be formed of another material whichexhibits a different resistivity. Alternatively, some property of thematerial, such as, for example, porosity, may be altered from oneresistance segment 110A to the next 1110B. For example, in thermallysprayed conductive traces, the unit resistance may also be a function ofthe size of the droplets being sprayed to form the trace, as well asother properties associated with the bonding surfaces of such droplets.

Referring back now to FIGS. 1 and 2, as noted above, the network 100shown is exemplary, and numerous variations may be made in order toimplement the network 100 in specific systems or structures. Forexample, if such a network installed into a structure such as pipeline,or a section thereof, more conductors than just two may be desired so asto refine the resolution of the network 100 for locating a strain orother physical phenomena detected thereby.

Such a pipeline may include multiple lengths of twenty miles or longerbetween which lengths structures known as “pig traps” (for insertion andremoval of “pigs” as is known in the art) may be formed. Thus, it may bedesirable to extend a plurality of conductors for a length as great astwenty miles or more. Thus, using a twenty mile section of a pipeline asan example, it will become desirable to locate the situs of the detectedphysical phenomena within a given range of distance along that twentymile section. Such a network 100 becomes much more valuable when theresolution with regard to locating the situs of the physical phenomenais refined to within a physically searchable distance such as, forexample, tens of feet.

In determining how many conductors should be used for such anapplication, the number of resistance segments formed in a givenconductor and how many different unit resistance values may be assignedto the plurality of conductors must be known. It is noted that thenumber of different unit resistance values which may be used willdetermine the number base (i.e., base 10, base 8, etc.) will be used innumerically representing the unit resistance values of each resistancesegment.

With respect to the number of resistance segments, considering adistance of twenty miles and assuming a resolution of approximately plusor minus twenty feet, one may determine that there will be 5,280segments in a given conductor (i.e., (20 miles×5,280 feet/mile)/20feet/segment=5,280 segments)

To determine the number of different unit resistance values which may beused in a given conductor, the uncertainty with respect to theconstruction of the resistance segments must be considered. For example,considering electrical traces being used as conductors, the uncertaintyassociated with the cross-sectional area of the trace must beconsidered. The uncertainty in cross-sectional area of a conductivetrace may include combined uncertainties of both width and thickness (orheight). Additionally, uncertainty may be affected by the mode ofconstruction of the conductive traces. For example, building up aconductive trace by thermally spraying multiple layers (such as in FIG.5) has an affect on the overall certainty of the resultant height aswill be appreciated by those of ordinary skill in the art. Such valuesof uncertainty may be determined through statistical analysis,experimentation or a combination thereof as will also be appreciated bythose of ordinary skill in the art.

For sake of example, considering the uncertainty in the cross-sectionalarea of a conductive trace to be less than 10%, say for example 9.9%,one may determine that the maximum number of useful unit resistancevalues which may be assigned to the individual resistance segments of aconductor is ten (i.e., Max. #≦100/9.9≦10.1). Thus, the base number forthe above example would be base ten, or in other words, ten differentunit resistance values may be assigned to resistance segments of aconductor.

Knowing that 5,280 resistance segments will be used, and that tendifferent unit resistance values will be used, one may determine thenumber of conductors which will be needed to provide 5,280 uniqueconcatenated digit strings for the identity groups. It is desirable thatthe unique concatenated digit strings each represent a prime numbersince the use of a prime number guarantees the ratios of all the unitresistance values represented thereby will be unique. For example,considering a four digit prime number of “ABCD”, each ratio of A:B, A:C,A:D, B:C, B:D and C:D will be unique. It is noted that no concatenateddigit string should include a zero digit, as an electrical trace may notbe constructed to include a resistance segment having a unit resistancevalue of zero.

The number of prime numbers available for a particular digit string maybe determined using one or more of various algorithms or databases knownand available to those of ordinary skill in the art. For example, theUniversity of Tennessee at Martin has published various lists of primenumbers including a list of the first 100,008 prime numbers (alsoreferred in the publication as “small primes”). Such a list allows forthe determination of the number of nonzero primes up to six digits inbase ten. Using such a database or publication it may be determined thatthe number of five digit nonzero primes is 6,125. Thus, five conductorsmay be used to formed a network of 5,280 resistance segments perconductor (and thus 5,280 identity groups with associated concatenateddigit strings) with each resistance segment being twenty feet long.

The operation of the five-conductor network would then be similar tothat described above with respect to FIGS. 1 through 3 whereinresistance changes would be detected with associate ratios of suchresistance changes being compared to a database of ratios associatedwith the 5,280 identity groups to locate a situs of strain or some otherphysical phenomena. Of course, it is noted that, while the use of afive-conductor network may be adequate for coding an resolution issuespresented above, it may be desirable to provide one or more conductors(e.g., a six- or seven-conductor network) for fault tolerance purposes.Thus, with fault tolerance, even if a conductor within the networkfails, adequate coding will remain in place to sufficiently identify,locate and quantify a physical phenomena.

It is also noted that the resolution may be improved over a given lengthby either improving the uncertainty associated with the construction ofthe conductors, or by including a greater number of conductors. Forexample, the number of conductors in the above scenario may be increasedto obtain a resolution of plus or minus ten feet, five feet or less ifso desired.

Referring back to FIG. 5, it is noted that either in conjunction with anetwork 100 (FIG. 1), or independent therefrom, conductors 104 and 106may be attached to a structure 120 for use in carrying other signals andmeasuring other values associated with the structure 120. For example,one or more sensors 150 or other microinstrumentation may be attachedto, or embedded in, a conductor 104 and 106 for purposes of measuring ordetecting pressure, temperature, flowrate, acoustic signals, chemicalcomposition, corrosion or data transmission anomalies. Conductors 104and 106, such as the conductive traces described above herein, have theability to extend for substantial distances (e.g. several miles) withoutsubstantial degradation in signal transmission. Thus, one or more ofsuch conductors may also be utilized as a communications link if sodesired.

As shown in FIG. 6, such traces or other conductors 104 and 106 may beinstalled in a conduit 122 or other structure in a predeterminedgeometric arrangement so as to detect strain or some other physicalphenomena at various locations within the structure. For example, FIG. 6shows a plurality of conductors 104 and 106 angularly displaced about acircumference of the conduit 122 and configured to coextensively andlongitudinally extend with the length of the conduit 122. Such anarrangement allows for detection of a strain or other physicalphenomenon which occurs on only a portion of the structure.

Thus, a plurality of networks may be disposed on a single structure.Alternatively, individual conductors might be spaced about thecircumference with each carrying one or more sensors therewith. Ofcourse other geometrical configurations may be utilized. For example,one or more networks (or alternatively, individual conductors) may beconfigured to extend from one end of a conduit 122 to another in ahelical pattern about a circumference thereof.

It is noted that the exemplary embodiments set forth above may beincorporated into any number of structures including stationarystructures well as mobile structures. For example, such a system couldbe employed in bridges, dams, levees, containment vessels, buildings(including foundations and other subsurface structures), aircraft,spacecraft, ground transport vehicles or various components thereof.Indeed, the system may be utilized with virtually any structure whereindetection, location and quantification of a specified physical phenomenais required.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the inventionincludes all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

1. A method of monitoring a structure comprising: attaching a pluralityof laterally adjacent conductors to the structure; defining eachconductor of the plurality to include a plurality of segments coupled inseries, each segment having an associated unit value representative of adefined energy transmitting characteristic; defining a plurality ofidentity groups, each identity group including a plurality of laterallyadjacent segments wherein each identity group includes at least onesegment from each of the plurality of conductors; transmitting energythrough each of the plurality of conductors; monitoring each of theplurality of conductors for changes in the defined energy transmittingcharacteristic; and comparing a first change in the defined energytransmitting characteristic in at least one conductor of the pluralitywith a second change in the defined energy transmitting characteristicin at least one other conductor of the plurality.
 2. The methodaccording to claim 1, further comprising determining a specific identitygroup from which the first change in the defined energy transmittingcharacteristic and the second change in the defined energy transmitingcharacteristic were initiated.
 3. The method according to claim 2,wherein determining a specific identity group includes determining aratio of the first change in the defined energy transmittingcharacteristic with respect to the second change in the defined energytransmitting characteristic.
 4. The method according to claim 3, whereindetermining a specific identity group further includes comparing theratio of the first and second changes in the defined energy transmittingcharacteristic to a plurality of predetermined ratios, wherein theplurality of predetermined ratios includes ratios of unit values of theplurality of laterally adjacent segments within each of the plurality ofidentity groups.
 5. The method according to claim 2, further comprisingcomparing the first change in the defined energy transmittingcharacteristic with the unit value or the segment which is both locatedwith the specific identity group and formed in the at least oneconductor.
 6. The method according to claim 5, further comprisingcomparing the second change in the defined energy transmittingcharacteristic with the unit value for the segment which is both locatedwith the specific identity group and formed in the at least one otherconductor.
 7. The method according to claim 1, wherein defining aplurality of identity groups includes assigning the unit values to eachof the plurality of laterally adjacent segments of each identity groupsuch that each identity group may be identified by a concatenated digitstring representative of the unit values contained therein.
 8. Themethod according to claim 7, wherein defining a plurality of identitygroups further includes assigning the unit values to each of theplurality of laterally adjacent segments of a given identity group suchthat each of a plurality of ratios of the unit values assigned to theplurality of segments within the given identity group is unique.
 9. Themethod according to claim 7, wherein defining a plurality of identitygroups includes assigning the unit values to each of the plurality oflaterally adjacent segments of a given identity group such that theconcatenated digit string is a prime number.
 10. The method according toclaim 1, wherein attaching the plurality of conductors to a structureincludes forming a plurality of conductive traces on a surface of thestructure.
 11. The method according to claim 10, wherein the forming aplurality of conductive traces on a surface of the structure includesthermally spraying the conductive traces on the surface of thestructure.
 12. The method according to claim 11, wherein attaching theplurality of conductors to a structure further includes spraying a layerof insulative material on a surface of the structure and forming theplurality of conductive traces over the layer of insulative material.13. The method according to claim 10, wherein defining each conductor ofthe plurality to include a plurality of segments includes defining aplurality of resistance segments and further comprising defining theunit value of each resistance segment to be representative of a unitresistance value.
 14. The method of claim 13, wherein monitoring theplurality of conductors for a change in the defined energy transmittingcharacteristic includes measuring resistance across each conductor ofthe plurality under no-load conditions to establish a baseline value foreach conductor and detecting a variance from the base line value. 15.The method of claim 14, wherein monitoring the plurality of conductorsfor a change in resistance further includes setting a new baseline valuefor each conductor after detecting the variance.
 16. The method of claim1, wherein monitoring the plurality of conductors for a change in thedefined energy transmitting characteristic includes measuring thedefined energy transmitting characteristic across each conductor of theplurality under no-load conditions to establish a baseline value foreach conductor and detecting a variance from the base line value. 17.The method of claim 16, wherein monitoring the plurality of conductorsfor a change in the defined energy transmitting characteristic furtherincludes setting a new baseline value for each conductor after detectingthe variance.
 18. The method according to claim 1, wherein monitoringthe plurality of conductors for a change in the defined energytransmitting characteristic include monitoring at a sample rate ofapproximately once per second.
 19. The method according to claim 1,wherein the transmitting energy through each of the plurality ofconductors includes inducing an electrical current in the plurality ofconductors.
 20. A method of monitoring strain induced within astructure, the method comprising: attaching a plurality of laterallyadjacent conductors to the structure such that a strain exhibited by thestructure will be substantially transferred to the plurality ofconductors; defining each conductor of the plurality to include aplurality of resistance segments, each resistance segment exhibiting anassociated unit resistance value and each of the plurality of conductorsbeing configured to exhibit a change in resistivity upon experiencing astrain therein; defining a plurality of identity groups, each identitygroup including a plurality of laterally adjacent resistance segmentswherein each identity group includes at least one resistance segmentfrom each of the plurality of conductors; transmitting energy througheach of the plurality of conductors; monitoring the plurality ofconductors for changes in resistance therein; and comparing a firstchange in resistance in at least one conductor of the plurality with asecond change of resistance in at least one other conductor of theplurality.
 21. The method according to claim 20, further comprisinglocating a situs of the strain exhibited by the structure by identifyingthe specific identity group from which the first change in resistanceand the second change in resistance were initiated.
 22. The methodaccording to claim 21, wherein identifying a specific identity groupincludes comparing a ratio of the first change in resistance withrespect to the second change in resistance to a plurality ofpredetermined ratios, each of the plurality of predetermined ratiosbeing associated with a one of the plurality of identity groups.
 23. Themethod according to claim 22, further comprising determining a magnitudeof the strain exhibited by the structure by comparing the first changeof resistance to the associated unit resistance value of the resistancesegment which is both located in the specific identity group and formedin the at least one conductor.
 24. The method according to claim 20,further comprising at least partially defining the associated unitresistance to each resistance segment of the plurality by defining thecross-sectional area of each resistance segment.
 25. The methodaccording to claim 20, further comprising at least partially definingthe associated unit resistance of each resistance segment by definingthe porosity of each resistance segment.
 26. The method according toclaim 20, further comprising at least partially defining the associatedunit resistance segment by selecting the material composition of eachresistance segment.
 27. The method according to claim 20, furthercomprising identifying each identity group with a concatenated digitstring representative of the associated unit resistance values of eachresistance segment contained therein.
 28. The method according to claim27, further comprising assigning the associated unit resistance of eachresistance segment of each identity group such that each concatenateddigit string is a prime number.
 29. A system for detecting physicalphenomena in a structure comprising: a plurality of laterally adjacentconductors, each conductor including a plurality of segments having anassociated unit value representative of a defined energy transmissioncharacteristic; and a plurality of identity groups, each identity groupincluding a plurality of laterally adjacent segments including at leastone segment from each conductor, wherein each segment within an identitygroup exhibits an associated unit value such that the unit values ofeach identity group may be represented by a concatenated digit string ofthe unit values and wherein each identity group exhibits a uniqueconcatenated digit string relative to each other identity group.
 30. Thesystem of claim 29, wherein each concatenated digit string isrepresentative of a prime number.
 31. The system of claim 29, whereinthe plurality of conductors is configured to be attached to the surfaceof a structure.
 32. The system of claim 29, wherein each segment isconfigured to exhibit a change in the defined energy transmissioncharacteristic upon experiencing a strain therein.
 33. The system ofclaim 29, wherein a plurality of ratios are defined between theassociated values of each segment of a given identity group and eachother segment of the given identity group and wherein each of theplurality of ratios within the given identity group are unique.
 34. Thesystem of claim 29, wherein the plurality of conductors comprises aplurality of conductive traces.
 35. The system of claim 29, wherein theassociated unit value of each of the plurality of segments correspondsto a cross-sectional area exhibited thereby.
 36. The system of claim 29,wherein the associated unit value of each of the plurality of segmentscorresponds to a material porosity thereof.
 37. The system of claim 29,wherein the associated unit value of each of the plurality of segmentscorresponds to a material composition thereof.
 38. The system of claim29, wherein each segment comprises a length of approximately twentyfeet.
 39. The system of claim 29, wherein each conductor comprises alength of approximately twenty miles.
 40. The system of claim 29,wherein the plurality of conductors includes at least five conductors.